Nick Stuart wears the uniform of a career civil servant: navy trousers and pale blue shirt. But his tie has multicoloured stars with prints of flags, his belt is African print, and socks red with black spots. It's hard to imagine a man with such outlandish, patterned accessories staying in the background, but that's how he's spent a 40-year career - quietly, at the heart of England's education policy.

From 1985 to 2001, Stuart worked in the education department, moving from one senior civil service post to another, including principal finance officer, deputy secretary for schools and then director general for employment and lifelong learning.

He was there when Kenneth Baker picked his office in the department's Sanctuary buildings in Westminster. He led the first pilots of league tables. He is credited by many as the architect of the 1988 education reforms, which introduced a national curriculum and grant-maintained schools and abolished the Inner London Education Authority. Yet his name is barely known outside Whitehall circles.

Stuart has never sought a public profile. "People used to say I was the architect of the 1988 [Education] Reform Act. I say I was clerk of the works," he says.

He has now been appointed chair of the Specialist Schools and Academies Trust, a position previously held for nearly 20 years by Sir Cyril Taylor - a vocal adviser on schools to successive governments. We meet in the SSAT headquarters at London's Millbank.

Stuart came to the civil service after an aborted attempt to be a sports journalist. His father was a BBC foreign correspondent, stationed around the world for much of his childhood. Stuart went to boarding school, then Oxford, and his dad got him some interviews with Fleet Street editors, who told him to go and work for the Carlisle Post. He married young, at 20, and, with small children, couldn't afford to be a trainee, so he went into the civil service.

Retirement jobs

Since retiring in 2001, he has held dozens of posts, from the QCA board to chair of Niace, the National Institute of Adult Continuing Education, and now the SSAT. The trust was set up 25 years ago as a network for city technology colleges, and has expanded and evolved with the development of academies and now federations of schools. More than 90% of state secondaries in England are members of the SSAT, as well as 400 primaries and 1,700 schools abroad.

Since Taylor stepped down in 2007 the trust's 40-strong council has been replaced by a board of 12. It has also moved sharply away from work directly funded by the government to contract work, competitively bid for. Four years ago 60% of its funding was directly from government; now it is just 15%.

What does the SSAT actually do? "We facilitate networks of schools, for mentoring, sharing and developing leadership. We have a headteacher-run strategy group. We compete for contracts, but we also speak to government," says Stuart.

For schools, the SSAT is a membership organisation where people can meet at conferences and share ideas. But, increasingly, the SSAT has acted as a consultancy, competing for contracts with Capita, Tribal, CfBT and PricewaterhouseCoopers. Last week, the SSAT won a £16m contract to train teachers for the roll-out of diplomas. The scale of what it is doing has earned it the nickname the "shadow DCSF".

"We're not here just for business purposes - just to win resources. We are one of the fastest growing charities. To survive and prosper we need to pay our way," says Stuart.

As a former civil servant who has been through past recessions, he is clear about what the education system is facing: "There is a phoney war between the parties about expenditure. The reality is that any future government will have to make cuts, and we'll have to do more for less." Does that mean organisations like his will be starved of resources? "I certainly think the SSAT and Niace will find themselves in choppier waters."

To navigate these waters the SSAT is preparing expansion: abroad, but possibly into primary and further education too. If the Conservatives implemented their plans for primary academies, it would fit the SSAT model neatly. Stuart says the model of academies will also have to adapt to survive the recession. "I suspect that the academies of the future won't be in sparkling new buildings," he says.

"Academies are not about buildings, but recreating a school with new leadership and dynamism. With sponsors, it's not now so much about the money as about giving a new vision and improving management."

We speak about the 1988 act - what worked and what didn't. He is proud of the national curriculum, but critical of the way league tables panned out. "Testing and the tabulation of Sats results has had difficult effects for primary schools and I'm conscious of the extent to which the last year of primary education concentrates on teaching to the test instead of expanding young people's minds. That has undoubtedly been a disadvantage."

He says he hopes the government's forthcoming plans for school-by-school report cards could be an important development towards solving this.

If he had the chance to rewrite the 1988 act now, what would he do? Stuart speaks passionately about lifelong learning and how it has been abandoned. He reveals details of Niace's upcoming review, which will argue that with changing demographics, lifelong learning has to become as important as initial schooling. He would like to give local authorities a stronger role in co-ordinating work between schools.

Asked what he'd do about admissions, he laughs. "I gave that up long ago. It's a completely intractable problem. A long time ago, I went to Stockholm and they could not fathom why children here don't go to the local school and we could not fathom why they did. It seems impossible for schools in this country to shake off the history of the grammar divide, even now. It has enormously affected choice."

On the highly political subjects of academies, league tables and admissions, Stuart clearly feels uncomfortable. "I don't want to be one of the civil servants who comes out of the woodwork to criticise governments," he says. And with that he slips back into Whitehall mode.